Pneumatically actuated stapling device

ABSTRACT

IN A PORTABLE PNEUMATICALLY ACTUATED STAPLING DEVICE AN AIR CHAMBER COMMUNICATING WITH A SOURCE OF COMPRESSED AIR IS LOCATED AROUND A CYLINDER WHICH ENCLOSES A RECIPROCABLE PISTON. IN AN AXIAL WEB OF THE SIDE WALL OF THE CYLINDER AN AIR PASSAGE IS PROVIDED THE UPPER END OF WHICH HAS A CONNECTION WITH THE AIR CHAMBER OF THE DEVICE AND IS PROVIDED WITH CONTROL MEANS WHICH IS ALTERNATIVELY RESPONSIVE TO AIR PRESSURE IN THE AIR CHAMBER AND IN THE INTERIOR OF THE CYLINDER. THE LOWER END OF THE AIR PASSAGE ADJACENT THE CYLINDER BOTTOM IS CONTROLLED BY AN AXIALLY MOVABLE BYMPER WHICH IS PROVIDED WITH VENT PORTS AND KEPT UNDER THE PRESSURE OF THE AIR CHAMBER. DURING THE PISTON WORKING STROKE THE BUMPER CLOSES THE LOWER END OF THE AIR PASSAGE AND OPENS THE VENT PORTS. AT THE END OF ITS WORKING STROKE THE PISTON ABUTS THE BUMPER WHICH IS PRESSED DOWNWARD AND OPENS THE AIR PASSAGE, WHEREBY COMPRESSED AIR IS ADMITTED TO THE LOWER FACE OF THE PISTON, WHICH RETURNS IT TO ITS INITIAL UPPER POSITION.

Sept. 20, 1971 v 1;, KQRTH 3,605,559

PHEUMATICALLY ACTUATED STAPLING DEVICE Filed Aug. 18, 1959 3 Sheets-Sheet 1 FIG. 2

INVENTOR Jz'rgen Karl/l ATTORNEYS Sept. 20, 1971 J. KORTH PNEUMATICALLY ACTUATED STAPLING DEVICE 3 Sheets-Sheet 2 Filed Aug. 18, 1969 llllllll "Ill 'I'II 0 I I I I I n I I n w MM WZ fimq m; w 7% Sept. 20, 1971 J. KORTH PNEUMATICALLY ACTUATED STAPLING DEVICE Filed Aug. 18; 1969 3 Sheets-Sheet 5 FIG.9'

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United States Patent 3,605,559 PNEUMATICALLY ACTUATED STAPLIN G DEVICE Jurgen Korth, 7 Birkenweg, 3001 Berenbostel, Germany Filed Aug. 13, 1969, Ser. No. 851,000 Int. Cl. Fb 13/042; F01b 11/02 U.S. Cl. 91-398 8 Claims ABSTRACT OF THE DISCLOSURE In a portable pnuematically actuated stapling device an air chamber communicating with a source of compressed air is located around a cylinder which encloses a reciprocable piston. In an axial web of the side wall of the cylinder an air passage is provided the upper end of which has a connection with the air chamber of the device and is provided with control means which is alternatively responsive to air pressure in the air chamber and in the interior of the cylinder. The lower end of the air passage adjacent the cylinder bottom is controlled by an axially movable bumper which is provided with vent ports and kept under the pressure of the air chamber. During the piston working stroke the bumper closes the lower end of the air passage and opens the vent ports. At the end of its working stroke the piston abuts the bumper which is pressed downward and opens the air passage, whereby compressed air is admitted to the lower face of the piston, which returns it to its initial upper position.

DESCRIPTION The invention relates to a stapling device actuated by compressed air, particularly for driving nails, pins, clamps, staples, dowels, etc. into a work piece.

In certain prior art stapling devices, the housing of the device encloses an air chamber which communicates with a source of compressed air and surrounds the working cylinder wherein a piston is movable in both directions. By means of a control valve assembly compressed air from the air chamber is admitted to the upper end of the working cylinder whereby the piston is actuated to perform its working stroke. The air displaced by the piston during its working stroke is admitted to and stored in another chamber adjoining; and the working cylinder. After completion of the working stroke this air flows back into the working cylinder below the piston and returns the same to its initial upper position. Part of the energy of the compressed air is lost for work by storing the displaced air in the adjoining chamber since the piston must compress the air in said adjoining chamber in order to build up enough pressure for its return stroke. Furthermore, the adjoining chamber of the working cylinder diminishes the effective volume of the air chamber to such extent that the pressure of the air contained therein decreases extensively during the working stroke of the piston. This has the undesirable effect of rendering the stapling device less efficient. In addition, said adjoining chamber of the working cylinder necessitates increased structural size and expense, and the resultant portable pneumatically actuated stapling device is less convenient to handle.

The object of the present invention is to provide a pneumatically operated stapling device which overcomes the aforementioned disadvantages and maintains high efficiency.

Another object is the provision of a portable stapling device which is easy to handle and convenient in operation. These and other objects, features and advantages of the present invention are set forth in the following de- Patented Sept. 20, 1971 tailed description in connection with the accompanying drawings which illustrate by way of example two embodiments of the present invention.

In the drawings:

FIG. 1 is a side elevation of a portable pneumatically actuated stapling device,

FIG. 2 is a cross section along the line IIII of FIG. 4,

FIG. 3 is a partial longitudinal section along the line III-III of FIG. 2,

FIG. 4 is a longitudinal section of the device showing the starting position of the piston before beginning its working stroke,

FIG. 5 is a partial longitudinal section of the device during the working stroke of the piston showing the halfway position,

FIG. 6 is a partial longitudinal section showing the position of the parts at the end of the working stroke of the piston,

FIG. 7 is a partial longitudinal section showing the position of the parts at the beginning of the return motion of the piston,

FIG. 8 is a partial longitudinal section showing the position of the parts during the return motion of the piston,

FIG. 9 is a section similar to FIG. 8 showing a farther advanced return motion of the piston, and

FIG. 10 is a longitudinal section of another embodiment of the invention, wherein the control means is constructed as a piston slide valve surrounding the working cylinder.

In a preferred embodiment of the invention an axial web of the side wall of the working cylinder encloses an air passage the lower end of which leads to the inside of the working cylinder adjacent its bottom Wall. The upper end of said air passage has a connection with the air chamber of the device and is provided with control means which is alternatively responsive to air pressure in the air chamber and in the interior of the working cylinder to control air flow through the air passage for returning the piston after a working stroke.

The device according to the invention comprises, furthermore, a resilient bumper which is movable in an axial direction and is located adjacent the bottom wall of the working cylinder. This bumper is'provided with apertures for venting the working cylinder and via an air duct permanently is kept under the pressure of the air chamber.

It is particularly advantageous to use as control means a differential valve piston the upper face of which is larger than the lower face and communicates with the interior of the working cylinder, whereas the lower face of said valve piston via an air duct communicates with the air chamber. The bumper limits the movement of the working piston and is movable within a stepped recess at the bottom of the working cylinder, which stepped recess limits the movability of the bumper. The air passage for admission of the compressed air which returns the piston to its initial or upper position opens into the interior of the stepped recess and therefore is intermittently closed by the movable bumper. An annular shoulder of the bumper engages an annular slot at the bottom wall of the working cylinder and is kept, in this way, at all times under compressed air pressure since a duct or bore connects the annular slot with the air chamber.

The omission of the prior art adjoining chamber allows the volume of the air chamber to be increased so that during the working stroke of the piston the pressure in the air chamber decreases less rapidly. Furthermore, no impact energy is lost by storing and compressing the air displaced by the piston during its working stroke in an adjoining chamber. Additional power is obtained by completely venting the air during the working stroke of the piston from the space underneath the piston immediately into the ambient atmosphere. As the volume of compressed air for the return motion of the piston is limited by the control means in the air passage in the web of the cylinder side wall, the piston is kept under full pneumatic pressure during only a portion of its return motion and, therefore, is prevented from abutting the cylinder cover too forcefully. At the same time the use of compressed air is economized permitting highly efiicient and inexpensive operation of the fastener device embodying the present invention.

Referring now to FIGS. 1 to 9 of the drawings, the portable stapling device embodying the present invention consists of a working cylinder :1 in which a driving piston 2 is movable in both directions. At the end of each working stroke the driving piston abuts a resilient bumper 3 located adjacent the bottom wall of the working cylinder 1. The side wall of the working cylinder 1 comprises a rib-shaped reinforcement or web 4 which encloses an air passage 5. Said air passage 5 is arranged in an axial direc' tion and communicates at the bottom of the working cylinder with its interior. The upper end of air passage 5 is provided with a control means 6 comprising a differential valve piston, the upper face 8 of which is larger than the lower face 10 and slidably covers a radial passage 9 leading to the interior of the working cylinder 1. Compressed air can be admitted directly from a compressed air supply chamber 26 enclosed by the body housing of the device to the air passage 5 and communicates with the smaller lower face 110 of the control means via a radial port 11 in the rib 4 of the cylinder side wall. The annular resilient bumper 3 includes an annular supporting member 34 disposed in a recess 17 in the lower end of the side Wall of the cylinder 1, and the supporting member 34 has a depending annular skirt or shoulder 14 which is provided with apertures 12 for discharge of the air displaced by the piston 2. During its working stroke said apertures $12 communicate with a ventilating slot 13 extending parallel to the axis of cylinder 1 and leading to the atmosphere (FIGS. 4 and 5). In this way, any air which is displaced by the piston 2 during its working stroke is removed from the space underneath the driving piston 2 and vented to the atmosphere.

The shoulder 14 is movably received in an annular slot 15 provided at the bottom wall of cylinder 1 and communicating via a secondary duct 16 with the air chamber 26, whereby the bumper 3 is always acted upon by air pressure in the chamber 26. The bumper 3 is movably guided in the direction of the cylinder axis by movement of the member 34 in the stepped recess 17.

O-rings 18, 19 protect the control mechanism 6 and 0- rings 20, 21 protect the bumper 3 against any possible loss of compressed air. The driving piston 2 is sealed against the interior side wall of cylinder 1 by an O-ring 22 and is maintained in its initial upper position by means of a permanent magnet 24 arranged in a cover plate 29 of cylinder 1.

An annular slide valve or cylinder valve 25 is movably arranged in the cover plate of cylinder 1 and in the initial lower position of the valve 25 as shown in FIG. 4, a resilient sealing ring 33 carried by the valve 25 closes admission of air from the air chamber 26 to the upper end of cylinder 1 and to driving piston 2. In this position communication is established between venting apertures 27 of the cylinder cover plate 29 and the space above the driving piston 2. The annular slide valve 25 is sealed against its guide bushing 28, and the cover plate 29 is sealed against the body housing of device by means of sealing rings 30 whereby any leakage of compressed air is prevented. Secured to piston 2 is a driver plate 31 which in the conventional manner during the working stroke of piston 2 drives staples into a Work piece.

As is well known in the prior art, the space above the slide valve 25 is connected by a passage 32 with a conventional control valve (not shown) which is operated by a trigger level 35 (FIG. 1.) In the initial or unactuated position of the trigger-operated control valve, the passage 32 is connected to the air chamber "26, and the pressure of the air from chamber 26 acts upon the upper surface of the slide valve 25 and holds it in the lower position, as shown in FIG. 4, whereby the resilient sealing ring 33 closes the upper end of the cylinder 1. At the same time the bumper 3 is held in its uppermost position by air pressure from the chamber 216 acting through the duct 16, thereby efiecting closure of the lower end of the passage 5 by the member 34. Since the interior of the cylinder 1 is vented to the atmosphere through the bumper 3, the apertures 12, and the slot 13, it will be understood that the differential piston valve of the control means 6- is normally held in its uppermost position (FIG. 3) by the air pressure from the chamber 26 acting through the port 11 against the lower valve face 10.

When the trigger lever 35 is actuated to initiate an operation cycle, the trigger-operated control valve (not shown) connects the passage 32 to the atmosphere. As the air pressure acting on the upper surface of the slide valve 25 is thus relieved, the pressurized air in the chamber 26 acts upon the lower surface of slide valve 25 and moves it to the position of FIG. 5. Whereby the venting apertures 27 of the cover plate 29 are closed. Air is admitted to the upper face of the piston 2 which, due to the compressed air pressure, is moved in a downward direction and by the time the piston 2. has moved past the passage 9, air pressure acting upon the larger upper valve face 8 of the differential valve piston causes the latter to move downwardly to close oif the upper end of the passage 5. At the end of its downward movement the piston 2 abuts bumper 3 which, in turn, is pressed downward by the impact momentum and opens the lower end of air passage 5 and closes the apertures 12 and the slot 13 (FIG. 6). Nearly at this moment the trigger-operated control valve (not shown), either auto matically or in response to release of the trigger lever 35, reconnects the passage 32 with the air chamber 26, and the annular slide valve 25 is pushed downwardly and blocks any further supply of compressed air to the upper end of the working cylinder 1 (FIG. 7). In this way the venting ducts 27 and the space above the driving piston 2 communicate with one another and thus diminish the air pressure therein. However, as soon as the pressure existing in the space above the driving piston 2 be gins to decrease, the differential valve piston of control mechanism 6 is pushed upwardly by means of the pressure of the air from air chamber 26 which acts through the port .11 on the lower valve face 10. As soon as the differential valve piston is thus returned to its initial upper position, pressurized air from the chamber 26 flows through the passage 5 (now open at both ends) into the space underneath the driving piston 2 tending to move it upwardly to its initial position as shown in FIG. 8

As soon as the driving piston 2, having just been pushed upwardly, slides over the radial passage 9, compressed air is able to act on the upper face 8 of the differential valve piston of control mechanism 6 and presses it donwardly to close the upper end of the passage 5. Thereby additional admission of compressed air into the space underneath the driving piston 2 is prevented and the volume of compressed air used for the return movement of the piston is limited. Said compressed air is sufiicient to push driving piston 2 for the remainder of the return motion against the magnet 24, whereby piston 2 is held in its returned position. Consequently piston 2 has reached again its initial position, as can best be seen from FIG. 4. During the latter portion of the return movement of the piston 2, the pressure in the cylinder 1 diminishes sufficiently so that the bumper 3 is returned to its original FIG. 4 position by the air pressure in the duct 16, thereby venting the lower end of the cylinder 1 and closing the lower end of the passage 5. When the cylinder 1 is completely vented, air pressure from the chamber 26 acting through the port 11 against the valve face returns the differential piston valve to its upper position, as seen in FIG. 4.

The invention is of particular importance in connection with compressed air operated hand appliances for driving of staples and other fastening means and has, in addition to the advantages of low weight and small dimensions, also that of low manufacturing costs.

It is apparent that the examples shown above have been given solely by way of illustration and not by way of limitation and that the invention is subject to many variations and modifications. All such variations and modifications are to be included within the scope of the appended claims.

What I claim is:

1. A pneumatically actuated stapling device comprising a body portion including a cylinder having a side wall with first and second ends and an end wall at said first end, a piston reciprocably movable in said cylinder, a compressed air supply chamber in said body portion, cylinder valve means for admitting compressed air from said air chamber to said second end of said cylinder for moving said piston in a working stroke from a position adjacent said second end of said cylinder to a position adjacent said first end of said cylinder, air passage means in said body portion having one end communicating with said air chamber and its other end communicating with said first end of said cylinder to admit compressed air into said first end of said cylinder for effecting a return stroke of said piston, a pneumatically operated control valve comprising a differential piston controlling air flow from said air chamber directly to said one end of said air pasasge means, said differential piston being in pressure communication with the interior of said cylinder and with said air chamber, air outlet means in said first end of said cylinder for discharging air from said first end of said cylinder to the atmosphere during the working stroke of said piston, movable bumper means provided in said first end of said cylinder for limiting the working stroke of said piston, and means normally urging said bumper means to a position closing said other end of said air passage means during said working stroke, said bumper means being movable by said piston at the end of said working stroke to a position closing said air outlet means and opening said other end of said air passage means for said return stroke.

2. A pneumatically actuated stapling device comprising a body portion including a cylinder having an upper end and a lower end, a side wall and a bottom wall, a piston reciprocably movable in said cylinder, a compressed air supply chamber in said body portion, means for admitting compressed air from said air chamber to the upper end of said cylinder for moving said piston from an initial position adjacent said upper end of said cylinder to a terminal position adjacent said bottom wall of said cylinder and at the end of its driving stroke, and port means adjacent said bottom wall for admitting compressed air to said lower end of said cylinder for eifecting return of said piston after terminating its working stroke, an air passage in said body portion having an upper end for communicating with said air chamber and a lower end communicating with said port means, pneumatically operated control means communicating with the interior of said cylinder and with said air chamber, said control means being operative to connect said air chamber to said upper end of said air passage for initiating a return stroke, air outlet ducts in said bottom wall for the discharge of air displaced from said lower end of said cylinder to the atmosphere during the Working stroke of said piston, an axially movable bumper provided at said bottom wall for limiting the stroke of said piston, and valve means carried by said bumper for closing said air outlet ducts during the return motion of said piston.

3. The device as in claim 2, further comprising a web on said side wall of said cylinder, said control means and said air passage being located in said web, and said air chamber extending around said web of said cylinder.

4. The device as in claim 2, wherein said control means communicates with the interior of said cylinder between said ends thereof, whereby said piston is supplied with full pressure compressed air for only a portion of the return stroke.

5. The device as in claim 2, wherein the axially movable bumper includes a supporting member extending into said bottom wall of said cylinder and having apertures for venting to the atmosphere the air displaced by said piston during its working stroke, said supporting member having a shoulder communicating with said air chamber, whereby said bumper is permanently acted upon by the pressure of the compressed air in said air chamber.

6. The device as in claim 2, wherein the control means comprises a diiferential valve piston having two faces, the larger face of said diiferential valve piston communicating with the interior of the cylinder and the smaller face communicating with said air chamber, whereby said differential valve piston moves in response to air pressures acting on said faces to control the air supplied from said air chamber to said air passage and, hence, to said lower end of said cylinder.

7. The device as in claim 6, further comprising a step like recess at said lower end of said cylinder side wall and opening to the interior of said cylinder, said bumper being movably guided in said recess.

8. The device as in claim 7, wherein said bumper includes a supporting member, and said bottom wall provides an annular slot, said supporting member being engaged in said annular slot, and said annular slot being in communication with said air chamber.

References Cited UNITED STATES PATENTS 3,396,636 8/1968 Bade 91404 3,479,926 11/1969 Hillier 91-404 PAUL E. MASLOUSKY, Primary Examiner US. Cl. X.R. 

